The equation of the line is given by
y = mx + c
where m is the gradient of the line
c is where the line cuts the y-axis
x & y represent coordinates on the line.
The gradient m can be obtained as follows:
m = (5 - 8) / (5 - - 10) = (-3) / (15) = - 1/5
To obtain c, we use any known coordinate on the line and substitute it as well as the gradient in the general equation for the line.
Taking coordinates (5,5)
5 = (- 1/5)(5) + c
5 = - 1 + c
c = 6
Hence, the equation for this line is
y = -x/5 + 6